1. Field of the Invention
The invention relates to a device for the plasma-activated vapor coating of large surfaces with high coating rates. The large-surface substrates to be coated can be sheets of plastic, glass or metal, or also strip materials such as plastic films, pre-coated papers or textiles and small-area bodies arranged on large transport frames. Typical uses are the application of reflecting, reflex-reducing or decorative layers and the production of abrasion protection layers, corrosion protection layers or barrier layers. In most cases very adhesive layers of great thickness are necessary, which layers can only be deposited with the aid of plasma-activated processes. With high vapor deposition rates, correspondingly high plasma densities are necessary in order to obtain the desired effects of the plasma activation.
2. Discussion of Background Information
It is known and for various technological reasons often necessary to use arc discharge plasma sources to produce high plasma densities (see, e.g. EP 0 545 863 B1; EP 0 666 933 B1). Due to the spatial limitation of such arc discharges, to coat large surfaces the substrates have to be moved over the coating device, and several arc discharge plasma sources have to be arranged next to one another perpendicular to the movement direction of the substrates.
It is further known to use a magnetic field aligned in the movement direction of the substrates and parallel to the axis of the plasma sources to increase the plasma expansion in the movement direction of the substrates (EP 0545 863 B1: EP 0 666 933 B1; DE 196 12 344 C1; DE 196 12 345 C1). Moreover this magnetic field is used to increase the plasma density near the substrate surface and, in the case of electron beam vapor deposition, to decouple the arc discharge plasma from the high-energy electron beam necessary for the evaporation.
The arrangement of several arc discharge plasma sources next to one another perpendicular to the movement direction of the large-surface substrates inevitably leads to a certain nonuniformity of the plasma density perpendicular to the movement direction of the substrates. It was therefore suggested to cause a horizontal alternating deflection of the arc plasma by alternating magnetic fields, thus improving the uniformity of the plasma perpendicular to the movement direction of the substrates. Although in this manner on average a substantial increase of the uniformity of the plasma can be achieved, at high coating rates and high transport speeds very high alternating deflection frequencies must be used in order to avoid undesirable fluctuations of the layer properties in the movement direction of the substrates or in the direction of the surface normals. This requires relatively expensive solutions for the alternating deflection systems, and special time deflection programs are necessary for an optimum uniformity.